diff --git a/CMLibCommon.cmake b/CMLibCommon.cmake
index 70e78f4..1851fd0 100644
--- a/CMLibCommon.cmake
+++ b/CMLibCommon.cmake
@@ -5,6 +5,10 @@ if(CMAKE_INSTALL_PREFIX STREQUAL PROJECT_BINARY_DIR)
   message(FATAL_ERROR "Cannot install into build directory")
 endif()
 
+if(CMAKE_INSTALL_PREFIX STREQUAL PROJECT_SOURCE_DIR)
+  message(FATAL_ERROR "Cannot install into source directory")
+endif()
+
 include(CMLibDisableInSourceBuild)
 include(CMakeParseArguments)
 include(GNUInstallDirs)